1. Field of the Invention
The present invention relates to a bus bar wiring board forming an internal circuit of an electric connection box used in wiring of an electric mounting circuit of an automobile, etc.
2. Description of the Related Art
With respect to a bus bar wiring board in a related art, a desirable wiring pattern can be formed by punching a thin sheet metal. Further, a tab terminal (a terminal for connection to an external circuit) can be simply formed by folding an end portion and an intermediate portion of the bus bar wiring board. Accordingly, the bus bar wiring board is used in many cases as a constructional member of an internal circuit of an electric connection box together with a printed wiring board.
Tab terminals of the bus bar wiring board punched in a desirable pattern are respectively formed in an end portion and an intermediate portion of this bus bar wiring board by folding processing. Electric contact portions are respectively formed as a semi-spherical or semi-cylindrical embossed projection in the tab terminals. In general, the electric contact portion having a semi-spherical shape is called a bead and the electric contact portion having a semi-cylindrical shape is called an indent.
Before the tab terminal is folded, the bus bar wiring board is punched from an unillustrated thin sheet metal and is entirely flat. Thereafter, the flat tab terminal is folded by a supporting die described later and a press die constructed by a pressing die.
However, when projecting directions of the electric contact portions and a folding direction of the tab terminal are equal to each other as in the tab terminal and a contact face of the above supporting die coming in contact with the tab terminal is a flat face, the electric contact portions interfere with this contact face and the tab terminal can not be accurately folded at a perpendicular angle.
Therefore, the supporting die constituting the press die is conventionally formed in a concave shape which does not interfere with the electric contact portions at a folding time of the tab terminal.
A concave groove of one stripe is formed in the supporting die at its center. A width of the concave groove in a short side direction thereof is set to be wider than a width a of each of the electric contact portions in a direction perpendicular to a longitudinal direction of the tab terminal.
A procedure of the folding processing of the tab terminal in the conventional bus bar wiring board is processed in a manner that the tab terminal is folded in the same direction as a projecting direction of each of the electric contact portions. The supporting die is arranged on a folded portion of the tab terminal. The pressing die is raised from below the tab terminal so that the tab terminal is folded.
At this time, the electric contact portion is inserted into the concave groove of the supporting die. The tab terminal comes in close contact with a contact portion of the supporting die without any clearance, and is perpendicularly folded.
However, the above-mentioned conventional bus bar wiring board has the following problems since the concave supporting die is used when the projecting direction of each of the electric contact portions and the folding direction of the tab terminal are equal to each other as in the tab terminal.
Firstly, since the folded portion of the tab terminal is simply formed in the shape of a flat plate, a portion of the tab terminal corresponding to the concave groove is folded without any support so that a folding accuracy is reduced when the concave supporting die comes in contact with such a tab terminal and the tab terminal is folded.
Secondly, when a width of the tab terminal is narrow, a thickness of the contact portion of the supporting die must be correspondingly narrowed so that no sufficient strength of the supporting die can be obtained and no supporting die can be constructed.
In such a case, even if the supporting die can be constructed, a contact area of the contact portion in the folded portion is reduced if the thickness of the contact portion of the supporting die is reduced. Accordingly, the folding accuracy of the tab terminal is greatly reduced.
Thirdly, a problem exists in that the above problems can be solved by changing the folding direction of the tab terminal or the projecting direction of each of the electric contact portions, but much labor and cost are required to change these directions.